A price paid by humanity for an upright posture and for a habitat including supporting surfaces both painful and injurious to an unprotected human foot is the necessity of wearing footwear. Footwear protects the soles of a wearer""s feet from the ground surface, the balance of a wearer""s feet from other environmental influences, and simultaneously is viewed as a means of ornamentation and sexually differentiated display. In addition to protective and ornamental functions, requirements already partly in tension, an item of footwear is desired to do minimum violence to a user""s pedal anatomy in the course of walking and standing, and simultaneously allow maximum possible freedom of movement so that the supple human foot may continue to function in a manner for which evolution adapted it, and possibly even move beyond the pedestrian in kinesthetic manifestation of physical talent. Simultaneously with an increasing flexibility in certain degrees or axes of motion however, as in bending in a posterior phalangeal or rearward toe or ball region, it may be desirable to reduce flexibility in other degrees of freedom, as in providing support or preventing collapse in a metatarsal region. The metatarsal region of a foot, or a corresponding region of a shoe, is also variously known as an arch or an instep region, with xe2x80x9cinstepxe2x80x9d more indicative of a shoe, and xe2x80x9carchxe2x80x9d more indicative of a foot.
Aforementioned manifold objectives of footwear function are of course partially in conflict, as may be observed from the marketing of ornamental or fashion shoes thought to be positively damaging to a user""s feet, however accepted by a sub-population of shoe wearers as a necessary expression of a fashion persona. Similarly athletic shoes, while possibly making a fashion statement in a limited context, are unsuitable for dress or office wear. Other similar tradeoffs may be observed between comfort and protection, comfort and fashion, and so forth, not to mention between cost of manufacture and quality of materials and construction. Add to these trade-offs variation in user taste, fitness, mass, life-style, gait, activities and budget, and it is clear that a product which expands the envelope of available design solutions along at least one product axis is likely to increase some consumers"" utility function, and hence constitute a new and useful addition to the foot-covering marketplace.
A demand exists for toddler""s and children""s footwear meeting a parent""s need for fashionable decoration of the toddler, while simultaneously allowing that child freedom and comfort of pedal movement, while avoiding repetitive stress injury to the foot. Given a product meeting these objectives, an efficient or simplified method of manufacturing obviously possesses additional economic utility.
It is an object of this invention to provide an improved article of footwear.
It is a further object of this invention to provide an efficient method of manufacture for an improved article of footwear.
It is a more particular object of this invention to provide an improved article of footwear providing superior flexibility in a posterior phalangeal region.
Yet a more particular object of this invention is to provide an article with superior flexibility in a posterior phalangeal region, also possessing adequate support in a metatarsal or arch region.
Another object of the invention is to provide such an article of footwear embodying aesthetically pleasing features.
More particularly, an object of the invention is to provide an article of footwear having an construction functionally adapted to meet the above requirements, which article is also aesthetically pleasing.
Still another object of the present invention is to provide a method of construction for an article of footwear in accordance with the above object, which method is economically efficient.
These and other objects of the present invention will be more readily comprehended by an inspection of the drawings and specification contained herein.
A shoe is constructed having an upper, and a composite sole comprising an innersole, a midsole, and an outersole. An innersole is essentially an insert, either free-floating or affixed to an interior or upper surface of a midsole, and is not regarded as part of the present invention. The primary function of an innersole is generally to provide additional cushioning between a bottom of a user""s foot and a remainder of the composite or multilayer sole, and, by variable thickness, more closely conform an innermost or upper surface of the composite sole with the bottom of the foot.
A midsole, unsurprisingly, is a structure intervening between an innersole and an outersole. In the present invention, a midsole is affixed to a lower periphery of the upper in a method of manufacture to be described more fully below. Finally, an outersole is affixed to a lower surface of the midsole as well as an exposed portion of the periphery of the upper. The outersole is that portion of the composite sole and of the shoe which directly contacts a ground surface during use, and is a relatively thick slab of rubberized plastic or other similarly flexible material, which by its bulk provides a dominant portion of a stiffness or elastic modulus of the shoe in bending and in twisting about major and minor principal axes; a lesser portion of the stiffness being provided by the upper. When confusion with xe2x80x9cinnersolexe2x80x9d is not likely, the midsole may also be known as an insole.
The sole or outersole of a shoe functions to cushion the user""s foot from small irregularities of a ground surface, such as pebbles, by distributing a resultant force concentration over a larger area of the bottom or sole of the user""s foot, while ideally maintaining sufficient local flexibility and shock absorption to avoid pivoting or rocking on the irregularities. The (shoe) sole also provides an overall structural integrity to the shoe, and constitutes a strongest member thereof.
Structural and cushioning functions of the outersole dictate a relatively thick and rigid structure, compared to other components of the shoe. This relative thickness and rigidity are however counterindicated by a requirement or objective of flexibility. It is thus a general feature of shoe design, and a particular feature of the present invention, that an intelligent compromise be achieved between requisite rigidities, flexibilities and cushionings.
A useful compromise is achieved in part between rigidity, flexibility and cushioning in accordance with the present invention by an indentation or grooving of a foresole or frontmost portion of the outersole. Forming a grid-like pattern or design on a bottom or ground-contacting surface of the outersole, the indentations or grooves permit a greatest degree of flexibility in bending about a horizontal axis perpendicular to a longitudinal or major principal axis of a user""s foot and shoe, a substantial degree of flexibility around this longitudinal axis, and simultaneously an incrementally negligible degree of flexibility about a vertical axis perpendicular to the longitudinal axis of the shoe or foot, thus preserving an overall shape of the shoe. Simultaneously a substantial degree of resistance to bending about a rearwardly parallelly displaced member of a series of horizontal axes perpendicular to the shoe""s longitudinal axis, is achieved by interposition of a brace or bridge spanning a gap between a heel and the foresole, as will be clear in the illustrations. This bridge simultaneously provides added support to a user""s metatarsal or arch region, while focussing bending about the described series of parallel axes in a region adjacent to a user""s toes, coincident with a natural hinge region of the human foot. It is believed that a unique pattern of grooves or indentations in the foresole region of the outersole, coupled with the action of a uniquely adapted bridge or tapered shank support extending through the metatarsal or arch region of the outersole, cooperating with a conventional heel shape, confers a unique and advantageous combination of flexibility and stiffness against bending in variously rotated and spatially displaced axes of the outersole, and confers a uniquely advantageous complex mechanical characteristic on the shoe of which the outersole forms a composite member.
A further flexibility is achieved in a show built in accordance with the present invention by elimination or moderation of unnecessary sources of stiffness in a construction of the shoe. In particular, an internal steel shank support is replaced with the tapered external shank support or bridge, as discussed above. Also, an insole board, a common feature in the conventional shoe making art for, in part, maintaining a shape of an upper prior to attachment to an outersole portion of an item of footwear, is eliminated by virtue of a technique of construction which sews an upper blank directly onto a flexible non-woven fabric midsole, prior to a glueing of a resulting form to the outersole.
A process to fabricate an upper from a blank, and a midsole, comprises a plurality of steps: A special use sewing machine, known in the art as a xe2x80x9c(toe) Cap Beat Creasexe2x80x9d machine forms a toe shape in a blank prior to a lasting process, to create a partially formed upper, or first stage upper preform. The Toecap Beat Crease or Toecap Crease machine is known in the industry, and models are available from the Ta Chung sewing machine company, of Taiwan, R.O.C., and Yao Han Industries co., Ltd, also of Taiwan; Shin-Chuang City, Taipei Hsien.
Following a formation of the toe shape or toe cap, a second special use sewing machine, known in the art as a xe2x80x9cDisc Feed Overseaming Machinexe2x80x9d is utilized to stitch the preform directly to the non-woven fabric midsole. A resulting second-stage upper preform is then subjected to a 100 to 110 degree stress relief/vulcanizing heat treatment in order to remove a shape memory of an original flat blank conformation. The preform is subsequently subjected to a controlled and rapid cooling rate in order to impress a new stress-free conformation or shape memory on a now substantially prefabricated upper, or upper form. Upper and outersole are now bonded by adhesive over essentially a complete intermediate surface to form a uniquely flexible unitary construction without a use of insole board, insole binding, or other techniques known in the art of shoe construction tending to add additional stiffness.
Remaining machines mentioned: Vulcanizing machines, disc feed overseaming machines, and chillers or automatic refrigerators are known in the industry, and available on the open market.